I have an external hard drive (Western Digital Red 3 TB, WDC WD30EFRX-68EUZN0) in a USB enclosure. Both the drive and the enclosure support SATA at 6 Gbit/s, and the enclosure is connected via USB super-speed (5000 Mbit/s). I'm copying files using rsync from my internal hard drive (Western Digital Red 6TB, WDC WD60EFRX-68L), and am getting a transfer speed of around 30 MB/s (240 Mbit/s?).

To me this sounds slow, considering SATA 6 / USB-SS support about 20 times that much?

If it is slow, what can I do to diagnose the problem and improve the speed?

Some additional information in response to @Ale..chenski: The enclosure has the name "Renkforce" printed on it. I think that is an "off-brand", belonging to the local semi-professional IT retailer where I bought it (Conrad.com).

so the chip is "JMS567", but I don't know whether that's good or not. At least it confirms that the bridge is supposed to deliver up to 6Gb/s.

The USB connector on the enclosure is labeled "USB 3.0" and it and the included cable are colored blue, which is the code for USB 3.0. So unless they are committing fraud, it quite clearly is a USB 3 device.

On the computer side it is connected to a blue USB outlet labeled "USB 3.0 / UASB" and the super-speed logo. KDE's KInfoCenter shows it as connected to an xHCI Host Controller with a speed of up to 5000 Mbit/s.

@Ale..chenski, wow, what certainty! ;) I didn't think writing what it is saying on the enclosure helps much, it's pretty generic, bought at the local IT store. But see the revised answer.
– A. DondaDec 27 '18 at 20:15

@Ale..chenski, ok, I added all the details on the enclosure to the question, and as far as I can tell your assertion "your enclosure operates at USB2 480 mbps" is quite unfounded.
– A. DondaDec 27 '18 at 20:28

1 Answer
1

Is the speed slow?

You're focusing on the theoretical maximum transfer speed, 6Gbit/s or about 750MB/s. I don't know about that particular hard drive, but I don't think physical spinning hard drives can approach anywhere near 6Gbit/second. It seems like 200MB/s would be a high average.

It can be hard to know if you've got a slow or fast drive, but comparing it to other identical drives should give you an idea. For your particular drive Amazon says 145MB/s is a typical transfer speed (not counting the buffer, and with no USB enclosure & overhead in the way).

Test the speed

Try some HD speed tests, to test & eliminate seek times - copying a particular file that happens to be fragmented, or just spread around the drive (I think some filesystems write files in "stripes", ext seems to).

Now what?

There's not much you can do to speed up your computer's USB. Try unplugging every other USB device and test again, or ensure you use fast hubs.

If you can remove the hard drive from it's USB enclosure, you could connect it directly to your computer via SATA, then test it's speed without the USB being "in the way."

If the speed is now within the average 145MB/s, then you know the USB enclosure is slowing the drive down, and if you want the best speed then don't use the USB enclosure, just directly connect the hard drive to your computer's SATA (or consider a hot swap hard drive bay).

Thanks for the tips, I will check them out. The problem is, with all benchmarking I don't really know what speed I can expect, and what the relevant tweaks are. Before I posted this question, I did a lot of searching, and one can get a lot of information on testing, and a lot of the possible tweaks, but no practical guidance as to a) what to expect b) which tweaks I should actually try – there are far too many to try them all.
– A. DondaDec 27 '18 at 20:33

I don't think it can be a fragmentation problem, at least on the destination side, since this was the initial backup to an empty ext4 system.
– A. DondaDec 27 '18 at 20:33

I don't accept your answer (yet), because you covered diagnosis (benchmark, connect directly), but not "is that slow?" and "what can I concretely do to improve it?" – Sorry in case these points weren't sufficiently clear.
– A. DondaDec 27 '18 at 20:35

"Is it slow" is a big question... that's hard to tell, but I'll edit in some ideas. The filesystem can make a big difference, sometimes I only see write speeds to one of my usb drives (with ext) of 0.3MB/s when the device itself supports ~3MB/s in a speedtest or accessing sdXN directly.
– Xen2050Dec 27 '18 at 21:12